This invention relates to vascular access systems implanted in individuals for the infusion of medication and the like, and particularly to vascular access systems which permit repeated introduction of medication into the device with minimal tissue damage to the individual.
In the treatment of many illnesses, it is necessary to repeatedly infuse medication directly into the bloodstream, into a particular organ, or otherwise to a particular medication site. For example, various chemotherapy regimes for treatment of cancerous conditions require frequent periodic medication. Bowel diseases and bone infections are other examples of conditions which require repeated treatment, as does the periodic dispensing of pain medication for terminally ill patients. In such frequent medication situations, to avoid having to locate a blood vessel for injection by needle each time, it is preferred to implant a catheter into the circulatory system through which the medication can be infused. Likewise, catheters are implanted to dispense medication directly to diseased or other treatment sites. Often, the medication is toxic in concentrated amounts and, therefore, must be infused through a catheter into a large volume of blood. To accomplish this, the catheter is fed through a vessel to a large vein or a chamber of the heart.
A problem that arises with some implanted vascular access systems is that, despite steps taken after they are used to keep them clean, the catheter may become infected. Given sufficient time, any catheter system which leaves the access opening external of the body will necessarily develop infection at the site where the catheter passes through the skin. While fully implanting a catheter device may reduce the problem of infection, other devices which are fully implanted require more invasive surgery, resulting in more discomfort, greater expense, and a longer recovery period. Moreover, these invasive techniques tend to form unsightly scars and scar tissue.
Various removable devices have been developed to administer medications to the large veins in the body or to a chamber in the heart, including external extending catheters, such as those referred to as BROVIAC, GROSHONG, and HICKMAN catheters. While there are differences between these external extending catheters, in the medical trade these various catheters are generally collectively referred to as BROVIAC-type catheters, or "BROVIACS." Another general type of system which is wholly implanted is generally referred to as a vascular port, such as, a for example, PORT-A-CATH.RTM., available from Pharmacia Deltec, Inc., in St. Paul, Minn., or as disclosed in U.S. Pat. No. 5,281,205 to McPherson, or VITAL-PORT.RTM. available from Cook Inc. in Bloomington, Ind.
The externally extending catheters are implanted using a guide wire, which is inserted into the body and directed to the point of application through the cannula of a large needle. Once the guide wire is in place in the body, a sheath is fitted on a dilator and guided down the guide wire by the dilator. When the dilator is withdrawn, the sheath forms a tunnel through the body to the point of application. The distal end of the catheter is then directed to the point of application through the sheath, leaving the proximate end of the catheter extending from the body. The sheath is formed from peel away sections, which are separated to remove the sheath and leave the catheter extending into the body to the selected treatment site.
Another prior art technique is referred to as a direct cutdown technique, in which an incision is made over the vein and the catheter is then inserted directly into the vein without use of a guide wire. The tunnel may be formed using a second cutdown or skin incision and a sharp tipped hollow metal trocar tunneling device.
An advantage of the externally extending catheters is that they can be inserted under light anesthesia on an outpatient basis. Furthermore, they tend to require less invasive procedures, requiring only a small incision in the skin. Moreover, the procedure is relatively quick. An external extending catheter can be implanted or removed in a matter of fifteen minutes or thereabouts. Moreover, the externally extending catheter can be used for numerous applications, such as chemotherapy, treatment of bowel disease, blood product infusions, bone infection, and can be used to administer pain medicines for terminally ill or seriously injured persons. However, the disadvantages of the externally extending catheter include a significant likelihood of infection at the point of exit from the body, an unsightly and somewhat intimidating medical device protruding from the body, and a restriction on the patient's activities. The patient cannot swim or engage in numerous other activities that would expose the catheter exit site to an even greater risk of infection.
Vascular ports eliminate some of the disadvantages of the externally extending catheters. Vascular ports are implanted beneath the skin and, therefore, eliminate some of the risk of infection. Furthermore, the patient is generally able to engage in most activities, including swimming. However, vascular access ports require a more invasive surgical procedure in order to implant or remove the port in or from the body. Conventional vascular ports require that a large incision be made in the skin and a cavity physically excavated below the skin to receive the port device. Moreover, the port is typically sutured to the muscle fascia. Once the port is in place and the delivery tubing is inserted and directed to the site of application, the incision is closed, leaving a relatively large scar site and protrusion of the skin at the port location. The medication is delivered to the port transdermally by a needle, which is pushed through the skin and into the chamber of the port through a membrane of material such as silicone. The disadvantage of the port is that it requires an invasive and more time consuming surgical procedure. Therefore, the procedure is, in general, significantly more expensive than the implanting of conventional externally extending catheters. Furthermore, when the port gets infected, the infection tends to be a large infection and requires similarly invasive procedures for removal of the vascular port.